At present, germanium (Ge) based photodiodes are used for optical to electrical conversion of signals in silicon (Si) photonics due to its lower bandgap of 0.7 eV, making it an optimum choice for the communication wavelengths of 1310 nanometer (nm) and 1550 nm. Some of the key performance metrics of photodiodes are low reverse leakage current, high optical responsivity (i.e., absorbing light and generating a larger amount of photo current) and higher bandwidth (i.e., speed of the operation). However, a known approach towards attaining a high speed photodiode design is a compromise between bandwidth and optical responsivity. The diode area is reduced to improve the bandwidth, but such a reduction in area impacts the optical responsivity. Another approach is to reduce the thickness of Ge, but thinner absorber material absorbs less light thereby limiting responsivity.
A need therefore exists for methodology enabling formation of a Ge-based photodetector without compromising between bandwidth and optical responsivity.